Full Idea
We may say not merely that this virus causes yellow fever, but also that it is 'the' cause of yellow fever; but we could only say that sweet-eating causes dental decay, not that it is the cause of dental decay (except in an individual case).
Gist of Idea
The virus causes yellow fever, and is 'the' cause; sweets cause tooth decay, but they are not 'the' cause
Source
J.L. Mackie (Causes and Conditions [1965], §3)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.47
A Reaction
A bit confusing, but there seems to be something important here, concerning the relation between singular causation and law-governed causation. 'The' cause may not be sufficient (I'm immune to yellow fever). So 'the' cause is the only necessary one?